FIG. 1 depicts vehicle 101, vehicle transceiver 102, and vehicle tracking infrastructure in the prior art. Vehicle 101 is a conveyance for people or things or both. Examples of vehicle 101 include cars, buses, trucks, etc.
Vehicle transceiver 102 is a telecommunications device that is present in vehicle 101. Vehicle transceiver 102 comprises a transmitter part and a receiver part. In addition to supporting other services (e.g., unlocking a car, etc.), vehicle transceiver 102 is used to provide a signal with which to determine the location of vehicle 101. A particular situation in which vehicle transceiver 102 is used is when vehicle 101 has been stolen.
Vehicle tracking infrastructure 103 receives signals wirelessly from vehicle transceiver 102. Using the received signals, vehicle tracking infrastructure 103 determines and tracks the location of vehicle 101. One or more radio-equipped base stations that constitute vehicle tracking infrastructure 103 receive signals from vehicle transceiver 102 after the transmitter part in vehicle transceiver 102 has been activated. In some cases, vehicle tracking infrastructure 103 transmits signals to vehicle transceiver 102 to activate the transmitter part.
Various stolen vehicle tracking systems exist in the prior art and can be grouped into two categories. The first category comprises proprietary tracking networks. The second category comprises cellular-based tracking networks. In some cases, the tracking networks have a Global Positioning System (or “GPS”) capability described below. An exemplary tracking system from each of the two categories is now described.
Lojack, a registered trademark of Lojack Corporation, Dedham, Mass., is a system that belongs to the proprietary category. Lojack enables police departments that are equipped with proprietary tracking computers to monitor the location of a vehicle, typically one that is stolen. A transceiver hidden within the vehicle is activated by a radio signal when the vehicle owner reports the vehicle to the police as being stolen. The transmitter part of the transceiver then emits a tracking signal that is monitored.
A disadvantage of proprietary-based tracking systems is that proprietary equipment costs are typically more than that of non-proprietary, standardized equipment. Also, proprietary tracking systems are not ubiquitously deployed and are often found mainly in major metropolitan areas where deployment is more cost-effective than in sparsely-populated areas.
OnStar, a registered trademark of General Motors, Detroit, Mich., is a system that belongs to the cellular category. The OnStar automobile navigation system uses cellular phone technology to send tracking information from a vehicle transceiver to the OnStar monitoring center that supports the vehicle. The vehicle transceiver contains a GPS receiver that continually obtains information from GPS satellites in orbit around the earth. These satellites transmit information which, when received and processed, provides the geographic location of the unit receiving the signals. The transmitter part of the vehicle transceiver transmits the GPS information to the monitoring center to determine the vehicle's position.
A disadvantage of the cellular-based tracking system is that it relies largely on cellular networks, which are optimized mainly for voice services. In tracking systems that use cellular networks, for each message transmitted, each connection between the vehicle transceiver and a base station serving the transceiver uses a frequency channel for an extended period of time. Although this type of network is acceptable for voice calls that use a channel for at least a few minutes at a time, it is suboptimal for handling relatively infrequent GPS messages at lower information rates. Another disadvantage is that the GPS signals from satellites cannot be received in certain environments such as indoor parking garages and tunnels.
What is needed is a vehicle tracking system without some of the costs and disadvantages in the prior art.